Question:

(a) Besides privacy, what other security functions does Pretty Good Privacy (PGP) provides?

(b) What is the Post Office Protocol (POP) used for? Why is it important that POP uses authentication, whereas the Simple Mail Transfer Protocol (SMTP) does not?

(c) When worms attack the e-mail client, the e-mail servers (the Mail Transfer Agent (MTA) and the Mail Delivery Agent (MDA)) get overwhelmed as well. Explain why.

(d) What do you meant by spam? Blocking lists are typically used to prevent spam. Discuss the effectiveness of using blocking list. How do ISPs prevent their clients from sending spam?

(e) What do you understand by the term Virtual Private network (VPN)? Describe how IPSec can be used to implement a VPN.

(f) Compare and contrast IPSec and SSH.